Showing papers on "Class (philosophy) published in 1989"

What does a conditional knowledge base entail

Abstract: This paper presents a logical approach to nonmonotonic reasoning based on the notion of a nonmonotonic consequence relation. A conditional knowledge base, consisting of a set of conditional assertions of the type "if ... then ...", represents the explicit defeasible knowledge an agent has about the way the world generally behaves. We look for a plausible definition of the set of all conditional assertions entailed by a conditional knowledge base. In a previous paper, S. Kraus and the authors defined and studied "preferential" consequence relations. They noticed that not all preferential relations could be considered as reasonable inference procedures. This paper studies a more restricted class of consequence relations, "rational" relations. It is argued that any reasonable nonmonotonic inference procedure should define a rational relation. It is shown that the rational relations are exactly those that may be represented by a "ranked" preferential model, or by a (non-standard) probabilistic model. The rational closure of a conditional knowledge base is defined and shown to provide an attractive answer to the question of the title. Global properties of this closure operation are proved: it is a cumulative operation. It is also computationally tractable. This paper assumes the underlying language is propositional.

Conceptualizing Social Structure: The Misuse of Classification in Structural Modeling

Abstract: forms that reduced structural patterns to almost geometric sets of relationships (Wolff 1950). Similar procedures are utilized by modem network theorists when conceptualizing connections between "nodes" in a social network. These uses are compatible with ours but at a more abstract level where virtually all behavioral content is removed and focus is on the formal or mathematical properties of the network. This content downloaded from 207.46.13.169 on Sat, 01 Oct 2016 05:29:04 UTC All use subject to http://about.jstor.org/terms 572 AMERICAN SOCIOLOGICAL REVIEW This points to the central and vital function of classification in the grand strategy of science. Its most important purpose is to allow us to generalize what we learn by the study of a few members of a category to other members of the same category. The ability to generalize includes the ability to predict. If we are able to say that something is a "member" of category "Y," and all Y's behave in such a fashion, then we can predict that the new object Y will behave in a similar fashion. But to make this procedure work optimally it must be grounded on valid structural models. These models represent how objects in nature are joined and how their parts operate in relationship to each other and, as a result, provide the basis for explanation and theory (Willer 1967; Bates and Harvey 1975). The purpose of classification, on the other hand, is to raise explanation to the level of a generalization to a class of similar objects. This is accomplished by a reiterative procedure in which a generalization in the form of a hypothesis is derived from a model and tested on a few selected members of a category. The ultimate success of the procedure depends upon preserving a clear distinction between concepts derived from classification, and those derived from modeling. If models are constructed using categories, the procedure becomes circular and selfconfirming. SUMMARY AND DISCUSSION The above argument is illustrated in Figure 1 which, from bottom to top, represents three levels of abstraction, each succeeding level moving further from the world of sense impressions. At the first level of abstraction, structural models of three separate groups are shown. Only three-person (position) groups are shown for the sake of simplicity. Let us assume they are all work groups of a similar type, for example, physicians' offices. Each group is represented symbolically by a set of geometric figures in a definite relationship to each other. The shape of the geometric figures represents the different positions and roles contained within each group. For example, the triangle represents the position of physician, the square the position of nurse, and the circle the position of office manager/secretary. Each geometric figure represents a unique position and is labeled by a subscript indicating, first, group location and, second, its identity in the group. The triangle or physician's position in group one is given the subscript 1,1 to indicate it is located in group 1 and is identified as position 1. In group 2, the physician's position is given the subscript 2,1, indicating it is position 1 in group 2, and so on. Inside each geometric figure the letters X, Y, and Z represent the actors occupying each position, and the subscript indicates group location. They could be read as Physician X1, Nurse Y1, Office manager Z1. The letters selected are arbitrary and they may represent a distinctive feature of the positional occupant such as sex, race, or other attribute. The double-ended arrows represent the unique relationships between actor-occupied positions and are designated by "R" with a triple subscript. The first number in the subscript indicates the group location, and the last two the positions in contact. For example, R112 indicates the relationship in group 1 between positions 1 and 2. It is important to note that each group is represented by a separate model involving particular people occupying particular social positions in association with each other in the context of different physicians' offices. These models would utilize concepts referring to unique social units and the relationships or connections that relate these units to each other to form an observable bounded whole. Although they are all "physicians' offices," in the real world they exist as separately occurring behavioral networks. Again, the purpose of these structural models is to furnish an analyst with a symbolic representation of an entity, a social group in this case, which can be used to formulate theories about how entity elements function in relations to each other. To formulate theories for scientific testing, attributes of the parts of the model or of their relationships to each other are examined in terms of how changes in one are related to changes in the others. In the middle section of Figure 1 we show three classification schemes of positions, relationships, and actors or position occupants. For example, all triangles are classified together as physician positions and assigned the symbol A, squares are classified together as nurse positions and assigned the symbol B, and so on. Relationships and occupants have also been classified and symbolically designated. This content downloaded from 207.46.13.169 on Sat, 01 Oct 2016 05:29:04 UTC All use subject to http://about.jstor.org/terms CONCEPTUALIZING SOCIAL STRUCTURE 573

Incomplete classifications of a finite set of objects using Monotone Systems

Abstract: The problem of incomplete classification is solved using a monotone system of a special kind. A classification method based on identification of the minimal cores of the monotone system is proposed. Existence conditions of a complete classification are given. The method is compared with previously published methods. Automatic classification methods, in addition to looking for complete classifications (i.e., partitioning of the initial set of objects), when classes are nonintersecting and form a covering of the entire set, also consider classifications with intersecting classes, with fuzzy classes, with macrostructure, etc. [1-3]. An independent group comprises incomplete classification methods, which identify a special class of “atypical” (background, special, or intermediate) objects and then assign the rest of the objects to nonintersecting classes [4-6]. Incomplete classifications are constructed when it is desirable to form classes comprising “strongly separated” subsets of objects, with all the background objects collected in a single class. This is archived either by two-step procedures, in which the first stage involving identification of the special objects is independent of the second stage involving classification proper, or by single-stage processing in which the classification functional is defined on the set of two-level classifications, thus complicating the discrete optimization problem. Moreover, both cases require specifying in advance the number of classes and the cardinality of the set of special objects, which leads to multi-alternative computations. Finally, most of the known algorithms are crudely approximate. In this paper, the sought incomplete classification is implicitly described by a separate estimate for each identified class of nonspecial objects, and this estimate should be extremal and equal on all classes of the sought classification. The proposed approach requires minimum prior information: we only need to know the measure of association of one object with a subset of objects. The number of classes and the number of objects identified, as special, is not fixed in advance. The proposed algorithm guarantees exact solution of the corresponding extremal problem.

Class ‐ a simple view

Abstract: The aim is to defend the starting‐point of Marx's theory of class, which is located in a definition of the working class in the Communist Manifesto. It is a definition solely in terms of separation from productive resources and a need to sell one's labour power, and it is closely connected with Marx's thesis that the population in capitalism has a tendency to polarize. That thesis conflicts with the widely‐held belief in the growth of a large middle class, unaccounted for by Marx. Moreover, recent critics such as Elster, Roemer, and Cohen have argued that this definition fails even in its own terms. The definition is refurbished so as to withstand these objections. But is there any point in using it? Does it serve to pick out the exploited producers as Marx intended? It does, once due attention is given to the idea of the collective worker, which is central in the volume of Capital which Marx himself published. That idea makes plain that it is an irreducibly corporate entity which is productive and subjec...

Teaching Writing: Motivating Inquiry.

Abstract: Consider the following two scenarios. Why is there such a difference between these two discussions, and what does the difference say about what approaches help or hinder students' learning? "We disagree with Carol's group," Dan said. "What this woman did doesn't go beyond the limits of freedom of speech." "Could you explain why?" I asked. This was the second day of an activity that is part of a series of lessons designed to teach eleventh-grade "regular" students some of the thinking strategies involved in writing extended definition essays. They had worked in small groups most of the previous day trying to determine whether twelve different incidents involving freedom of speech should be allowed under this right (George Hillocks, Jr., 1987, "Mode and Focus of Instruction: Teaching Procedural and Declarative Knowledge for Writing," Unpublished Study, U of Chicago). Now, we were discussing the incidents as a class and using them to develop a set of criteria to define freedom of speech. "Well," Dan began, "an airport is a public place, and freedom of speech guarantees a person the right to say what he wants in public as long as he doesn't, like, cause people to riot or harm anyone and.. ."

Incompleteness and Fictionality in Meinong's Object Theory*

Abstract: objects only, but a theory of all objects, existing and non-existing, real, possible and impossible objects. Only the important class of incomplete objects, which as a subclass contains the objects of fiction has been associated by him with a theory of universals as abstract objects. It seems to me that one of Meinong's most fruitful conceptions is his theory of incomplete objects which may be completed. This conception allows for the fact that we can elaborate on our concepts and ideas and that we do widen our knowledge of objects even if they are incomplete. The propositional attitude with which most of this work is done is not knowing or believing, which are directed towards the universe of actual objects, but assuming. That is why Meinong thinks that in all our intellectual efforts we have to go through assumptions. With the capacity of assuming any kind of object, according to the principle of the freedom of assumptions, we cannot only create objects but complete them, even if we cannot turn them into complete ones. How the completing is done depends on the field of work within our intellectual fabric, be it everyday work of imagination, phantasy, or plain thinking in the scientific enterprise, or work in the arts. In none of these and many other fields can we dispense with fictional objects, that is to say, with incomplete objects that serve as those objects which we try to use as starting points for further work. Clearly, the ontology of Meinong does provide us with what we may need when we do not want to reduce different kinds of objects to one another or when we are unable to reduce them: it is a rich ontology. But is it too rich? I do not think so, if we read it bona fide. It proceeds from experience or -if you like -preanalytic data to the explanation by theory, but it does not propound a theory which answers all the questions that can be raised. Surely, there remain many questions and quite a lot of them are difficult to answer. I mention only a few of them. The first question is how incomplete objects are related to the complete ones, like the object "Something Blue" (etwas Blaues) to the blue object which we see on our desk. The second is more general. How are we to view the relation between an incomplete object and its complete counterpart, if we use the incomplete and even fictional object to grasp the complete one? In other words, how is the incomplete object embedded or engraved in the real one, if the latter is the target of our acts of assuming, believing, or judging?

L(p) Regularity and Extrapolation.

Abstract: The goal of this thesis was to isolate classes of bounded linear operators in L P(I) which on the one hand still have some of the well-known and useful properties of positive operators, but which on the other hand are large enough to include some im portant classes of operators (e.g. the Hilbert transform and the singular operators derived from it) that cannot be dominated by positive operators. In Chapter I, we study as a first class of this kind the L p regular op­ erators. By definition such operators map equiintegrable sets in Lp(I) into equiintegrable sets in L P( I ) and sets compact in measure into sets compact in measure. We show that with respect to duality and pertubation theory they have properties similar to positive operators. In Chapter II, we study strongly Lp regular operators as the class of op­ erators, which preserves growth restrictions of Lp functions (formulated in terms of nonincreasing rearrangements of functions). We show that such op­ erators can be extended to bounded linear operators on certain Lorentz and Marcinkiewicz spaces. Many im portant operators in analysis are in this class since we can show that all interpolated operators are strongly Lp regular. Chapter III contains some representation theorems for linear operators in Lp( I ) by kernels of distributions, which are motivated by the representation of positive operators by stochastic kernels.

Particles, Pragmatic and Other

Abstract: This paper deals with problems in describing, from a synchronic point of view, certain "little words" in Modern Greek like άραγe ("I wonder"), δήθeν ("so-called", "as if"), τάχα ("so-called"), called "hesitation adverbs" by Triantaphyllidis (1978), in his standard grammar of Modern Greek first published in 1941. In previous work I have shown that this class of linguistic items is a rather heterogeneous set from a syntactic, semantic and pragmatic point of view and that not all of them express hesitation on the speaker's part. But if they do not all deserve the name "hesitation adverbs" how else can they be described? At least some of these little words can be (and have been, cf. Tzartzanos 1953) described as particles. However, Zwicky has recently claimed that "languages contain no 'par­ticles' but only words belonging to syntactic categories, clitics, and (inflectional or derivational) affixes” (Zwicky 1985: 294). Moreover, such little words have turned out to play an important role in pragmatic theories, as illocutionary force indicators, discourse markers, etc. Sometimes though, it is not sufficiently clear how the diversity of categories relates to the phenomena described or how the different categories relate to one another. Adequate answers to questions regarding the descriptive level as well as the relations between various descriptive categories used for such twilight zones of language is a necessary prerequisite for evaluating the different theories and the claims of universality with respect to such phenomena.

Generation And Understanding Of Natural Language Using Information In A Frame Structure

Abstract: Many expert systems and relational database systems store factual information in the form of attributes values of objects. Problems arise in transforming from that attribute (frame) database representation into English surface structure and in transforming the English surface structure into a representation that references information in the frame database. In this paper we consider mainly the generation process, as it is this area in which we have made the most significant progress. In its interaction with the user, the expert system must generate questions, declarations, and uncertain declarations. Attributes such as COLOR, LENGTH, and ILLUMINATION can be referenced using the template: " of " for both questions and declarations. However, many other attributes, such as RATTLES, in "What is RATTLES of the light bulb?", and HAS_STREP_THROAT in, "HAS_STREP_THROAT of Dan is true." do not fit this template. We examined over 300 attributes from several knowledge bases and have grouped them into 16 classes. For each class there is one "question" template, one "declaration" template, and one "uncertain declaration" template for generating English surface structure. The internal databases identifiers (e.g., HAS_STREP_THROAT and DISEASE_35) must also be replaced by output synonyms. Classifying each attribute in combination with synonym translation remarkably improved the English surface structure that the system generated. In the area of understanding, synonym translation and knowledge of the attribute properties, such as legal values, has resulted in a robust database query capability.© (1989) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.